Power supplies from scrap

Ugha · 2009-01-20 04:24

I've recently scrapped a DVD player and I found it contained a very nice looking power supply that provides
both +5v and +12v regulated.

My question is... how do I tell how much current it can supply? I'd try to figure it out myself but I have no
clue even where to start... do I look at the transformer? The voltage regulator? Can I measure something
with a multimeter or something?

I have a somewhat related second question... considering it has exposed contacts and high voltage caps,
I'd like to make the power supply somewhat safe... is there any problem with hot-gluing it into a container
that seems somewhat airtight?

Last question... I promise... There's some brownish substance on the power supply around one of the
large caps. I'm assuming that since the whole supply works and seems without any form of fault, its
not dried electrolyte but instead perhaps some form of glue holding the large cap onto the board...
Question is, could the whole thing work even if the main cap has umm... leaked? If so will the whole
thing fail or smoke or explode or something down the road if used? (If it'll help, I can provide pictures).

Sorry to be such a noob guys.... I'd appreciate any info.

Brian218 · 2009-01-20 05:07

High Ugha,

A quick and dirty way of estimating the power rating is to look at the voltage regulators.
If they're the TO-92 size, power rating is usually 100-150 mA.
If they're the TO-220 size, they can usually handle 1 amp, and maybe more (especially with heavy duty heatsinks).

You might also try googleing the make/model of the DVD player and try to find a service manual online. A service manual should have info regarding power ratings.

Hot melt glue should be fine.

A pict of the cap would be helpful. The brown stuff could be epoxy or a coating of some sort. If the cap is bad, the power supply might function fine unloaded, but perform poorly under load. It's unlikely to do anything like explode, but it could happen. If there's a question regarding the performance of the cap, you might consider replacing it. Electrolytic caps can gradually dry out over time.

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Mikerocontroller · 2009-01-20 05:27

This is quite a coincidence. I just scrapped a DVD player and salvaged the power supply. The large cap (22uF)
@400v on mine also has a blob of brown glue. Is your DVD a COBY DVD-224 by any chance? I'm sure COBY is
the "Yugo" of DVD players but .....I wonder if the PS is worth checking out?

kwinn · 2009-01-20 15:16

A power supply is always worth checking out unless you already have 10 or more gathering dust in your junk box!

mikediv · 2009-01-21 18:15

most of the time that brown goo you see is either flux or some kind of bonding agent used during assembly it usally appears around parts that get hot from normal operation I have a PS that have that goo ·and some circuit boards it always seems to appear around the parts that get warm its harmless take a screw driver power off of course and lightly scrape it it should come right off I just run the blade of my screwdriver around the solder joint where it collects and it just crumbs off.
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Ugha · 2009-01-23 20:59

Sorry about taking so long to reply on this thread, I lost my $#%#^% camera until this morning.

Brian218: I've had a hard time figuring out the voltage regulator... close as I can figure it has a UTCTL431 TO-92 regulator... I don't get how it can supply
+12, -12, +5, -5 and -25 with one regulator though.

Mikerocontroller: It's a GPX DVD player... basically a no-name brand. (box image attached) I picked it up extremely cheap at a surplus store a couple years back.

mikediv: I'm a little nervous about scraping it off, and if it seems to run fine with it on, I think I'll just leave the goop in place.

PS: Sorry about the poor picture quality of the second power supply image...I need a tripod.

Power supplies from scrap

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